This invention relates to an apparatus for deaerating condensate in a condenser, and, more particularly, a condenser for a steam turbine plant whose start up is shortened.
In a steam turbine plant, it is necessary to deaerate the condensate before it is fed as the feedwater to the boiler in order to prevent the boiler from being corroded by the gases, particularly oxygen, dissolved in the condensate. The oxygen concentration of the condensate in the condenser is about 8000 ppb when the plant is not operating. On the other hand in order to prevent the corrosion of the boiler, it is necessary that the oxygen concentration of the feedwater is less than around 8 ppb. In general, the condensate from the condenser is recycled to the condenser, while the inside of the condenser is depressurized to a vacuum by an air ejector in order to deaerate the condenser. With only this measure, however, it is difficult to make the quick start up of the plant possible.
In, for example, Japanese Laid Open Patent Publication, No. 78/72903, it is known that oxygen dissolved in the condensate is partially removed by heating the condensate before the condensate reaches a hotwell of the condenser. That is, after only part of the condensate is heated by heat pipes disposed in a container, thus heated condensate overflows from the container whose lower part has no opening. Additionally some part of the condensate flows or is directly supplied to the hotwell even without being led to the container. Accordingly, it still takes a long time to deaerate the condensate.
An object of the invention is to provide an apparatus for quickly deaerating the condensate in a condenser.
This object is achieved by providing within a hotwell of the condenser an open conduit to permit the condensate to flow to a covered conduit covered so that the condensate cannot flow therein without passing the open conduit, and by heating the condensate in the open conduit.
According to this invention, more oxygen can be dissolved from the condensate and be removed into a condensing part of the condenser without dissolved oxygen being transferred into the covered conduit together with the condensate. Additionally the whole condensate is heated, resulting in more efficient deaeration of the condensate.